| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 17°F | 34°F | 25°F | 3.1" |
| February | 18°F | 36°F | 27°F | 2.2" |
| March | 28°F | 50°F | 38°F | 2.7" |
| April | 38°F | 64°F | 50°F | 3.6" |
| May | 48°F | 74°F | 61°F | 4.2" |
| June | 58°F | 83°F | 70°F | 4.2" |
| July | 62°F | 85°F | 73°F | 4.5" |
| August | 60°F | 83°F | 72°F | 4.9" |
| September | 53°F | 78°F | 65°F | 4.0" |
| October | 43°F | 65°F | 53°F | 4.5" |
| November | 32°F | 52°F | 41°F | 2.6" |
| December | 22°F | 38°F | 30°F | 2.8" |
| Index | Cassopolis | Michigan | National |
| Air quality index | 39 | 69 | 42 |
| Pollution index | 1,797,130 | 4,161,606 | 2,726,193 |
| Measurement | Total |
| Days measured | 260 |
| Days with good air quality | 232 |
| Days with moderate air quality | 26 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Vandalia, MI | 387 | 37 | 26.0% |
| Simonton Lake, IN | 5,081 | 37 | 26.0% |
| Bristol, IN | 1,539 | 37 | 26.0% |
| Decatur, MI | 1,935 | 38 | 24.0% |
| Marcellus, MI | 1,140 | 38 | 24.0% |
| Cassopolis, MI | 1,684 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Rouse, CA | 1,684 | 49 | 2.0% |
| Knollwood, IL | 1,684 | 39 | 22.0% |
| Princeville, IL | 1,684 | 41 | 18.0% |
| East Helena, MT | 1,684 | 40 | 20.0% |
| Sturgeon Lake 154, AB | 1,684 | n/a | |
| Cassopolis, MI | 1,684 | 39 | 22.0% |
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